fix(matrix): preserve empty room overrides

extensions/matrix/src/matrix/accounts.test.ts

@@ -685,4 +685,50 @@ describe("resolveMatrixAccount", () => {
       },
     });
   });
+
+  it("lets an account clear inherited groups with an explicit empty map", () => {
+    const cfg = {
+      channels: {
+        matrix: {
+          groups: {
+            "!shared-room:example.org": {
+              allow: true,
+            },
+          },
+          accounts: {
+            ops: {
+              homeserver: "https://matrix.example.org",
+              accessToken: "ops-token",
+              groups: {},
+            },
+          },
+        },
+      },
+    } as unknown as CoreConfig;
+
+    expect(resolveMatrixAccount({ cfg, accountId: "ops" }).config.groups).toBeUndefined();
+  });
+
+  it("lets an account clear inherited legacy rooms with an explicit empty map", () => {
+    const cfg = {
+      channels: {
+        matrix: {
+          rooms: {
+            "!shared-room:example.org": {
+              allow: true,
+            },
+          },
+          accounts: {
+            ops: {
+              homeserver: "https://matrix.example.org",
+              accessToken: "ops-token",
+              rooms: {},
+            },
+          },
+        },
+      },
+    } as unknown as CoreConfig;
+
+    expect(resolveMatrixAccount({ cfg, accountId: "ops" }).config.rooms).toBeUndefined();
+  });
 });

extensions/matrix/src/matrix/accounts.ts

@@ -37,10 +37,14 @@ function selectInheritedMatrixRoomEntries(params: {
 function mergeMatrixRoomEntries(
   inherited: MatrixRoomEntries | undefined,
   accountEntries: MatrixRoomEntries | undefined,
+  hasAccountOverride: boolean,
 ): MatrixRoomEntries | undefined {
   if (!inherited && !accountEntries) {
     return undefined;
   }
+  if (hasAccountOverride && Object.keys(accountEntries ?? {}).length === 0) {
+    return undefined;
+  }
   const merged: MatrixRoomEntries = {
     ...(inherited ?? {}),
   };
@@ -203,6 +207,7 @@ export function resolveMatrixAccountConfig(params: {
       isMultiAccount,
     }),
     accountConfig?.groups,
+    Boolean(accountConfig && Object.hasOwn(accountConfig, "groups")),
   );
   const rooms = mergeMatrixRoomEntries(
     selectInheritedMatrixRoomEntries({
@@ -211,6 +216,7 @@ export function resolveMatrixAccountConfig(params: {
       isMultiAccount,
     }),
     accountConfig?.rooms,
+    Boolean(accountConfig && Object.hasOwn(accountConfig, "rooms")),
   );
   // Room maps need custom scoping, so keep the generic merge for all other fields.
   const { groups: _ignoredGroups, rooms: _ignoredRooms, ...rest } = merged;